Method of packaging food items



United States Patent 2,365,767 METHOD OF PAcKAcING Foon ITEMS Robert A. Gore, Terre Haute, Ind., assigngr, mesne N. Y .,a corporation of N ew'York" V NoDrawing, Application FfebruaryA, 1955 ia e'aezvt 8 Claims. 01. 99- 171) This invention relates to packaging. More particularly it relates to a method of on items packaged therein. i

Various thermoplastic films are used extensively for wrapping and packaging. In the protective packaging of foods particularly for poultry, meats, andme atfood products for frozen storage or storage under refrigerating conditions the covering must beskin tighfso' that there will be substantially no pockets of entrappedairbetween the covering andthe surface of the packaged item.

Bags made of shrinkable films of unvulcan'iz'ed rubber and certain types of saran provide tight coverings onitem's In use 'th e item was ins'erted'i'n the ba'gf' and after the open end had been sealed thepackage'was or less as'by'im inserted therein.

assignments, to Union Carbide CorporationiiNew York,

producing skin tight coverings 2,865,767 Patented Dec. 23, 1958 operation is to be performedat 102 C., the solution can consistj of 60 parts'off propylene glycol and 4.0 parts of water. It is, of course, "to "be understood. that a sc at ca.

capable of use at a higher'tempe'ratu recan' also. beus'edf at lower temperatures.

ture' is rna'intained'f The temperature of the liquid medium to which the bag is subjected as'ipreviously mentioned.- is above but below the "melting point of the polyethylene fil of which the bag is made.

microscop'l The shrinking of thebag is eflected in a relatively short period of'tirne. In general, immersion of the package in 'the s hrink'in g liquidfor. a period offs to 10 seconds will be sutficient. However, satisfactory. results have been obtained by maintaining the package immersed theishrinking liquidforapproximately 2'to 3 seeonds.

The liquid mediacontemplated by'this invention can be heated to and maintained at the desired terripereturn- (above 100 C; and below the melting point of the polyethylene film constituting the bag) without any bubbling or surging thereof. Because .of the quiescent state 'of the shrinking liquid'at the shrinking temperature, thefilm ing. Because of its excellent low temperature durability i it is admirably suited as a protectivepackagingmaterial for foods such as poultry, 'meat', and mat food" products for frozen storage 'or' storage under" refrigerating condii tions. However, in' general" 1 littleor no shrinkage when water. Recently there has" been produced a polyethylene" film which does shrinkwhen suddenlysubjected to boiling Water, but for someappli'c'ationsa greater shrinkage is desired. In addition, the Ibiibblin' water causedv wrinkling of the film.

An objectdf this' i nve ntion is to provide a new and novel method of shrinking polyethylene, film.

Another object of this invention is to utilize the aforementioned method in producing protective skin tight coverings.

Other and additional objects will become apparent hereinafter.

The objects of the invention are accomplished in generalby inserting the ite mto be packaged inapolyeth'ylene bag and after closing the -open'end 'shrinkingthebag by suddenly immersing the package in a liquid medium," more fully describedhereafter, at a temperature above" 100 C. but below the melting point of the polyethylene. Preferably before the open end of the bag is closed, the interior of the bag is evacuated.

In the preferred embodiment of the invention, an aqueous solution of propylene glycol constitutes the liquid medium in which the shrinking of the bag is obtained. The proportion of propylene glycol depends on the temperature at which the solution is to be used. Thus, if the shrinking operation is to be carried out, for example, at 105 C., the solution can consist of 80 parts of propylene glycol and 20 parts of water. If the shrinking subjected suddenly to boiling g action of the boiling constituting thebag will not wrinkle during the shrinking' operation fand a 'smooth' skin itightflcovering substantially freebf wrinkles be obtained. By' the use of the shrinking liquid: herein contemplated, no dulling salt is ftirmed on--the' "surfa ce of the bag. Moreoverfit,is

non-toxic and' does not in any way deleteriou'sly'iatfect. the film.

The shrinkable bag contemplatedby this invention can, be made by appropriately sealing one open end ofjse ani less o'rse am ed thin' walled tubing'with or without gussets as desired. Polyethylene tubing having a wall,thicikiitis}'s 4 or ere'andjpr'r with'i 'rl'the range. of .0005" to 10040" erably withiiifthe range a 0.0913." t ohqzz r haveb efefn usedl' The dimensions of the bags are such aswill permit.

quick and ready insertion .of' the item therein. andfuponfv shrinking tvni' i' ium ely conform to, the item ai1d"for',in a protective 'skin N0. "486 263,"filed Februa -yfl. 1955, which co mprises melt-extruding film forming polyethylene through an an a s nd laring, said u e; hi n the. p a i formative stage accordance with the formula Orifice opening=K (below ratio) whereinforifice opening is the ditfer'ence between the radii*of the inner and outer lips of the die and isat least} I sa e-seen t 1JK.} x a qi men .0018, andb'low"ratio; defiiiedas Flat width of flattened tubing Outer diameter of orifice is within the range of 3.5 to 8. After evacuating the interior of the package the open end of the bag is closed and the package suddenly immersed in a solution of 60 parts propylene glycol and 40 parts water at 102 C. for 2 to 3 seconds.

To more fully describe the invention, an illustrative .Also, propylene glycol, alone andi withoutwater, can be usedfprovide'd the desired temp The precise shrinki'rigt'emperature' ii'se'd depends on the film:"constituting, thev bag can -be"determined by empirical experin'ients. Usually the shrinking. temperature is approximately 8' degrees, (CI) lower than that at whichit he film wilklose its birefringence, en erved; nd s ed. N gel; P sms. ale 19?;- ee;

V ght'covering substantially 'fr'ee fo f,

application thereof for the}? packaging of eviscerated turkeys will now be described. W

After evisceration and chilling, excess moisture is permitted to drain olf the turkey which is then squatted, either in a squatting machine or by hand, to broaden the breast of the bird and to free-up the tendons in the hocks and wings so that appendages will lie close to the body of the bird and not protrude at awkward angles which cause bridging. and sometimes breakage of the packaging film.

The ends of the hocks are then fastened down close to the tail of the bird usually by tying with wire, cord, rubber bands, etc.

The bird prepared as just described is then inserted into a loose fitting bag made of polyethylene film produced by the method of the copending application previously referred to either by the use of a loading horn or chute or manually pulling the bag over the bird as a pillow case is pulled over a pillow. The breast of the bird is toward the seamed end at the bottom of the bag. The resulting package is then evacuated of air on standard evacuating equipment. As the air is evacuated, care is taken to insure the film is pulled in to conform to the body of the bird. The neck of the air evacuated package is twisted by spinning before removal from the air evacuator. The twisted neck is then secured in a closed position by means of a metal clip or other appropriate tie. The excess bag stock beyond the clip or tie is then clipped off.

The. package prepared as described immediately before is then suddenly immersed in a solution at 215 F. (102 C.) and consisting of 60 parts propylene glycol and 40 parts of water for 2 to 3 seconds. The immersion may be by hand, basket dip or any other convenient manner or equipment. Upon removal from the solution, the package is weighed and then subjected to quick freezing at the end of which the frozen bird is stored under appropriate conditions.

The bag intimately conforms to the contour of the bird and is smooth and substantially free of wrinkles. The surface of'the bag has a higher gloss than before the shrinking operation.

The invention is admirably suited for the packaging of other eviscerated poultry such as chickens, ducks, geese, pheasant, etc. for frozen storage as Well as meat food items such as whole meat loaves, smoked butts, whole pieces of sausage, whole cooked hams, smoked picnics (shoulder hams), bone-in and boneless smoked hams, sliced luncheon meats, sliced ham, sliced bacon, sliced sausage, whole slices or wedges of cheese, whole meat carcasses, fresh meat cuts such as chops, steaks, etc. for storage under refrigerating conditions.

The principles of this invention are also applicable to bags made of other thermoplastic films such as Pliofilm, saran, polymer modified vinyl copolymers, polyethylene terphthalate (Mylar), polymer plasticized or liquid plasticized polyvinyl chloride, etc. which exhibits little or no shrinkage upon sudden exposure to temperatures at or below 100 C. or to obtain a greater shrinkage than obtained upon sudden exposure to temperatures at or below 100 C. In connection with the aforementioned films, satisfactory results were obtained by suddenly submerging bags made thereof in a liquid medium of the nature hereinbefore described at 102 C. for 2 to 3 seconds.

Herein and in the claims the proportions are by volume. Since it is obvious that various changes and modifications can be made in the above description without departing from the nature and spirit thereof, this invention is not restricted thereto except as set forth in the appended claims.

I claim:

1. In a method of packaging food items with a skin tight covering the steps which comprise inserting the item to be packaged in a bag made of a plastic film and shrinking the bag to conform to the contour of said item by suddenly immersing the bag and contents in a liquid medium comprising propylene glycol at a temperature above 100 C. but below the melting point of the plastic and maintaining said bag and contents in said liquid medium until shrinkage has been effected.

2. In a method as set forth in claim 1 wherein the liquid medium consists of water and such quantity of propylene glycol as willproduce a solution which at the temperature of use is in a quiescent state.

3. In a method as set forth in claim 1 wherein the liquid medium consists of to 60 parts of propylene glycol and correspondingly 20 to 40 parts of water.

4. In a method as set forth in claim 1 whereinthe liquid medium consists of 60 parts of propylene glycol and 40 parts of Water at a temperature of 102 C.

5. In a method of packaging food items with a skin tight covering the steps which comprise inserting the item to be packaged in a polyethylene bag and shrinking the bag to conform to the contour of said item by suddenly immersing the bag and contents in a liquid medium comprising propylene glycol at a temperature above C. but below the melting point of polyethylene and maintaining said bag and contents in said liquid medium until shrinkage has been effected.

6. In a method as set forth in claim 5 wherein the liquidmedium consists of water and such quantity of propylene glycol as will produce a solution which at the temperature of use is in a quiescent state.

7. In a method as set forth in claim 5 wherein the liquid medium consists of 80 to 60 parts of propylene glycol and correspondingly 20 to 40 parts of water.

8. In a method as set forth in claim 5 wherein the liquid medium consists of 60 parts of propylene glycol and 40 parts of water at a temperature of 102 C.

References Cited in the file of this patent UNITED STATES PATENTS 2,376,583 De Poix May 22, .1945 2,538,002 Irons et al. Jan. 16, 1951 2,545,243 Rumsey Mar. 13, 1951 2,745,419 Slingerland May 15, 1956 OTHER REFERENCES Modern Packaging, September 1950, page 93.

The National Provisioner, November 14, 1953, page 38.

Refrigerating Engineering, February 1954, page 46.

The National Provisioner, October 2, 1954, page 80.

Frosted Food Field, October 1954, page 25.

Modern Packaging, November 1954, page 170.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,865,767 December 23, 1958 Robert A, Gore It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 58, for "(below ratio) read (blow ratio) Signed and sealed this 31st day of March 1959.,

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

1. IN A METHOD OF PACKAGING FOOD ITEMS WITH A SKIN TIGHT COVERING THE STEPS WHICH COMPRISE INSERTING THE ITEM TO BE PACKAGED IN A BAG MADE OF A PLASTIC FILM AND SHRINKING THE BAG TO CONFORM TO THE CONTOUR OF SAID ITEM BY SUDDENLY IMMERSING THE BAG AND CONTENTS IN A LIQUID MEDIUM COMPRISING PROPYLENE GLYCOL AT A TEMPERATURE ABOVE 100*C. BUT BELOW THE MELTING POINT OF THE PLASTIC AND MAINTAINING SAID BAG AND CONTENTS IN SAID LIQUID MEDIUM UNTIL SHRINKAGE HAS BEEN EFFECTED. 